The invention relates to a pressure measuring system having a line through which a fluid flows, the line having a line section in which, on a flattened outer side of the line, there is provided a diaphragm whose movement, characteristic of pressure changes, can be transmitted to a pressure sensor.
Such a pressure measuring system is disclosed by U.S. Pat. No. 5,392,653. Such measuring systems are used in cartridges of an aspiration system. In an aspiration system, liquid is sucked up by means of a pump. The pump may be a roller pump or a Venturi pump, for example. Irrespective of the pump used, because of the resistance opposed to the flow in the tubes or lines in the event of an occlusion at the end of the tube, a vacuum will be produced in the tubes or lines. In conventional systems, the tube system is connected directly to a pressure sensor via a T branch.
Now, such aspiration systems are used, for example, in the cataract operation and are used to suck up the lens fragments produced during the operation, together with an infusion liquid. The current operation technique is to attract such lens parts by suction with the instrument connected to the aspiration system, to hold them firmly, bring them into a suitable position and break them down by means of ultrasound and subsequently suck them up. In the process, during a certain time, an occlusion is necessarily produced, since the suction opening is blocked by lens parts. After that, a greater vacuum builds up in the interior of the aspiration system. When the occlusion is loosened, which generally takes place very quickly, the vacuum is dissipated and, in the process, draws infusion liquid after it which, during the aforementioned operation, can lead to collapse of the anterior chamber of the eye to be operated on.
This after-suction and collapse effect is primarily high when there is air in the aspiration line. The volume assumed by the air under vacuum is reduced abruptly when the occlusion breaks and draws a particularly great amount of liquid after it. In the case of the known method with the use of a T branch, the inclusion of air is inevitable. In addition, in the case of this operating principle, the aspiration liquid can come into contact with the pressure sensor. Since this pressure sensor cannot be sterilized, there is the possibility of contamination of the patient with bacteria coming from the pressure sensor if the practitioner flushes back during the operation, which is necessary during certain operation steps.
With the device according to U.S. Pat. No. 5,392,653, the inclusion of air can be prevented and contact between the liquid in the tube system and a nonsterilizable sensor element is avoided. For this purpose, a metallic disk is fitted permanently to the pressure measuring chamber. This disk is coupled to a force or displacement sensor by means of magnetic force.
This system has the disadvantage that geometric conditions differing sharply from the circular cross section of the line system, that is to say the aspiration tube, prevail in the pressure measuring chamber. Because of this it is difficult to fill the chamber completely with fluid, and the lens fragments that are sucked up often remain stuck in the chamber. It is not possible to use this tube system for reconditioning in the autoclave sterilizer, since there is no possibility of emptying it completely and rinsing out the lens fragments reliably.
On the basis of this prior art, the invention is based on the object of specifying a pressure measuring system of the type mentioned at the beginning which can be used for reconditioning in the autoclave sterilizer.
This object is achieved, for a pressure measuring system of the type mentioned at the beginning, by a device according to the present invention.
The fact that the diaphragm is nondetachably connected to a protrusion which points away from the line and has an extension which is oriented substantially transversely with respect to the longitudinal alignment of the line section means that the cross section of the line system can be kept substantially circular, with the corresponding rinsing advantages.
The fact that this protrusion has a hole, through which the extension projects in the shape of a pin, means that a force sensor can have the excursions of the diaphragm applied to it in a simple way, mechanically and simultaneously detachably.
Further advantageous embodiments are identified in the subclaims.